An integrated circuit (IC) die is generally packaged to protect the die from external contamination or physical damage. An IC package generally includes, among others, a substrate, a die placed on the substrate and a heat spreader placed over the die to dissipate heat from the IC package. The die may be assembled on the substrate in a flip-chip configuration or a wirebond configuration.
In the flip-chip configuration, the die is mounted on the substrate. The die is “flipped” when it is mounted on the substrate such that solder bumps on the die are positioned on corresponding contact pads on the substrate. In the wirebond configuration, the die is electrically coupled to the substrate via bonding wires. Signals from the integrated circuit die may then travel through the wires or solder bumps to the substrate.
As the die is mounted on the substrate, the substrate is formed first before the die is assembled on the fully formed substrate. Generally, a substrate is formed by multiple dielectric layers with a core layer sandwiched in between the dielectric layers. The core layer may provide mechanical support for the package structure when the die is mounted on substrate.
However, as demand for high speed applications grows, the core layer thickness is reduced to achieve better performance. In some instances, the core layer is entirely removed to obtain a coreless substrate. A coreless substrate is generally thinner and may provide better electrical performance. However, because the coreless substrate is thinner and does not include a stiff core layer, it may be more susceptible to warpage compared to a substrate with a core layer.